Walt’s powers – electromagnetic in nature. The Others wanted to see if he could basically fulfill the role that Desmond would end up having at the end of the series. For his ‘mind powers’, see What Is Island/Black Smoke below. -OR- under orders from Jacob, they wanted to test him to see if his powers would allow him to confront/battle the Smoke Monster/fake MIB.

Who built the 4-toed statue? (I thought that was taken care of a while ago, but keep seeing the question)
The statue was revealed a while back to have been built by the ancient Egyptians in the guise of Taweret, who as a god and not a human, couldn’t really be bothered to have feet just like a human. Wait? Egyptians? Yes, they made it to the island (remember, it isn’t stuck in a fixed, singular location on earth – think of Ben & Locke ending up in Tunisia when exiting the island), and discovered many of it’s secrets, but didn’t understand the full width/breadth of it all. Remember the heiroglyphics under the statue and in the tunnels around the temple? There must have been a pretty large Egyptian colony there at one point. What happened to them? Well… I’ll get to that.

What is the island/what is it’s purpose?
Jamie got me thinking about brains last night. We were talking about the Smoke Monster taking over people’s bodies (well, not taking over their bodies, as we clearly saw the discarded husks of those whose faces it wore) but taking over their visage, and how at one point he said that Locke had to be dead in order to impersonate him. We mentioned that once a person was dead, the smoke monster sort of mapped-out their synapses and brain pathways, and through that ‘mapping’ process is how it assumed it’s personalities over the eons. So I was thinking about this and the fact that the island never was really in one place, coupled that with the mirror-moon theory that I was fond of starting back when I started watching the show (season 4?).
Anyway, if you look at the patterns in the lighthouse station (Eloise’s pendulum lab under the church – which was the same church as last night’s finale), to me it looks like a CAT-scan. Now, I’m not saying that the island and it’s intense electromagnetic core are Earth’s brain, but more of a net or catcher’s mitt. As we all should know – and was pointed out several times on the show I think – energy can not be created or destroyed, just.. re-purposed. The island moving through space/time in tandem with the Earth – instead of letting our mental energy disperse after physical death it sort of catches/re-charges that energy and keeps it together in a similar pattern. That similar pattern – and intermingling on whatever frequencies our brains operate on – is the ‘afterlife’. There’s nothing religious about it, just giving a scientific-ish reason for what we perceive as ‘going into the light’ and heaven/hell. Heaven being a greater control over those energies (and ability to interact with other deceased brain patterns) like we saw at the end of the episode last night, Hell being what the smoke monster was for a lot of it’s existence – a disjointed consciousness without a full range of communication or ability to ‘move on’ and . What some people would call some kind of spiritual ‘soul’, in this case is just a remnant of your brain’s electrical patterns post-physical-death.

To me, at least after only thinking about this for a few hours after the finale, it kind of explains why those on the island could see dead people (or people who had spent time on the island and were off of it) – that radiation boosted the frequencies of their brain patterns so those interactions would be possible. The island itself – being a strong-ass-juggalo-crushing-magnet – helped concentrate these energies as it moved throughout space/time.

Why did the island need to be protected?
So those who sought to take control over not only physical presences but also control (or disperse) those electrical presences (aka ‘soul’) could not do so.

What would have happened if Smokey destroyed the island?
No island = no coherence for the deceased’s mental impulses. No coherence means no seeing dead people (or hearing their creepy-ass whispers on the island), but also no ‘afterlife’ as the electrical patterns making up our brains would dissipate.

What the hell is that big stopper thing?
Someone, maybe the ancient Egyptians that built the statue, dug into the island and released a shit-ton of energy. The cavern with the stopper had obviously been constructed to reverse that fuck-up and plug it in. Why a goofy-looking carved rock could do that.. uhhh.. drama? Whoever originally un-stopped the hole realized “oh shit, bad stuff is going on!” and plugged it back up, and being a long time ago didn’t think about fuckin’ magnets, just magic all up in this bitch.

What is the Smoke Monster?
The smoke monster is not the Man In Black. Jacob treated it like it was at times, but it was just like Smocke/(F)Locke – whatever you want to call him. The body was dead, and the Monster took over the deceased persons persona and molded itself to look like them. I’m saying that it is a highly concentrated cloud of elecro-magnetic energy that at some point became sentient, due to the island’s unique magnetic properties and maybe as a by-product of the island’s ‘purpose’ as stated above. I’m making a big assumption here, but whoever built the stopper realized that the black smoke that had been terrorizing the Egyptians (killing them/running them off the island) and whoever else could be trapped by the energies down in the “source” cave and lured it down there. That’s what the other bodies down in the cave were – whoever lured it in (and/or whoever built the shit). Smokey was trapped until dumbass Jacob threw his brother’s body down there, which screwed up whatever kind of magnetic balance there was. Smoke Monster roars out into freedom, later finds the Man In Black’s body, and maps the synapse pathways to ‘become’ him. Starts trying to kill Jacob to get off the island just like the original MIB wanted to. However, he can’t just use the donkey wheel that Locke/Ben used to leave the island, nor go into the source cave himself because he doesn’t want to become trapped again like he was prior to Jacob’s dumbassery.

Why do they all need to leave together/come back together – Why does Fake Locke need
I dunno, something to do with the law of Conservation of Energy (again), but I think using that is just a weak attempt at filling the writer’s plot holes. Maybe island-dwellers have a different electrical charge than the outside world and need to balance the equation to make it work out. Yet again, without knowing that kind of shit, it all gets distilled down to destiny and lots of people saying “We HAVE to _______”.

Why did The Others frequently have voices/whispers follow them around in the first few seasons but not later?
Well, either inconsistent writing, or something to do with the dead following them around because they were under orders from Jacob.

Why was Richard able to be immortal/why was the smoke monster able to take away that gift?
Advanced electrical impulses kept his cells from aging at the same rate as a normal person. Instead of there being midiclorians, Jacob’s fake-mom, Jacob, Jack, Richard, Hurley were all ‘touched’ at some point and had a massive amount of energy transferred into them. Coupled with hardly ever leaving the island, it came to appear like they were immortal. Immortal isn’t really the right word, but used for lack of better, more specific terminology. The whole deal with the cup and everything – pure ritual, didn’t mean shit. No one knew how to ‘let go’ of the energy stored inside themselves and pass it on without doing the ritual though.

So how could Jacob ‘bring’ people to the island?
All the Darma stuff wasn’t destroyed, he called Widmore literally. Other than that, since he was king of the biggest magnet in the world, I guess he could draw people in like fishing – just with a magnetic hook.

Why couldn’t babies be born on the island… but all of a sudden they could again?
Prolonged exposure to the island’s weird radiation screwed everything up. Claire hadn’t been on the island long enough to feel the effects and have her pregnancy complicated yet. Sun had her baby off-island after the effects had subsided. Jacob/MIB’s mom, much like Claire, delivered right after arriving. I guess it takes more than 2 months, as that’s the amount of time between Rousseau’s arrival and giving birth to Alex. I’m assuming that giving birth wasn’t really all that much of a problem prior to the incident that the Losties set off with the nuke in the 70s (the Dharma people had kids like Ethan)

Why were there heiroglyphs on the clock in the hatch?
Dharma just put it in to reference the Egyptian shit they’d seen on the island. It didn’t really mean anything other than “Hey dummy, there aren’t any numbers up on this sign now, pay attention!”

The numbers, what were they?
Didn’t we see that each one of the candidates were numbered in Jacob’s cave a few episodes back, and that the numbers correlated?
Feel free to point out bullshit or ‘oh duh, we all understood that part’ sections.

Dharma food drops
Ben and the Others killed off Dharma on the island, but Eloise left the island and took over Dharma’s operations (which is why she had her lamp post station). She was sending food back knowing – after shooting her future son and talking to jacob – that shit was going to hit the fan one day and whoever was on Jacob’s side was going to need all the help they could get. OR, Ben/Others just covered up what they did so that Dharma would keep supplying them while they built up their off-island business that purchased their sub and allowed them to recruit people like Juliet.